Search Results

Search Results

Download the accompanying student worksheet under "Downloads."
What did Earth look like 250 million years ago? Or 1 billion years ago? Or 4.5 billion years ago? EarthViewer is an interactive tool that allows you to explore the science of Earth's deep history.

(33 min 43 sec) The disappearance of the dinosaurs at the end of the Cretaceous period posed one of the greatest, long-standing scientific mysteries. This three-act film tells the story of the extraordinary detective work that solved it. Also available in Spanish.

(1 hr 27 min 59 sec) Earth has been both cooler and warmer in the past, but the change is usually gradual. The current rate of carbon dioxide increase is unprecedented in human history, and solutions to mitigate its effect on global warming are challenging to implement.

(1 min 18 sec) DNA has a double helix structure. If untwisted, DNA looks like two parallel strands. Each strand has a linear sequence of A, C, G, and T. The precise order of the letters carries the coded instructions. One strand is a complementary image of the other: A always pairs with T, and C always pairs with G.

(5 min 42 sec) Diversity-oriented synthesis (DOS) is a strategy used by chemical biologists to create a huge diversity of small molecules with potentially useful properties. A scientist working in Dr. Stuart Schreiber's lab shows us how engineering, computer science, chemisty, and biology are all used in DOS.

(1 min 20 sec) In diversity-oriented synthesis, many combinations of chemical building blocks undergo relatively few reaction steps to form a vast variety of different molecules. In this example, 45 x 45 x 45 combinations yield more than 88,000 novel molecules.

(1 min 35 sec) The hypothetical relationship of chemical space and biological space is plotted on a three-dimensional graph, giving a glimpse of the future direction of research at the intersections of various disciplines.

(1 min 10 sec) Rapamycin is a small molecule originally isolated from nature. It has antibiotic and immunosuppressive properties. It also allows two proteins which do not normally interact to bind together in the cell, which causes problems in the nutrient-sensing pathway.

(1 min) Microarray technology is useful for screening many small molecules at once. Automated devices have made it possible for thousands of different small molecules to be printed as an array of spots on a glass slide. A single type of protein which has been tagged with a fluorescent marker can then be washed across the array. Any small molecule that binds to the protein can be detected by scanning for spots that are fluorescent.

(1 min 57 sec) A molecular menagerie of small molecules is displayed, with two particular molecules singled out for attention: rapamycin and furrowstatin, which are discussed in the remainder of Dr. Schreiber's lectures on chemical genetics.

(6 min 9 sec) Without an appropriate catalyst some chemical reactions would be so slow as to appear not to occur at all on the human timescale. However, when catalyzed, these reactions can be very dramatic.

(5 min 7 sec) Air is an invisible gas as are hydrogen and helium. How can you tell if a balloon contains hydrogen? Hydrogen has particular physical and chemical properties that can be tested. Dr. Cech enlists student volunteers to show how a chemical reaction can be used to identify a substance.